Which of the following curves does NOT represent motion in one dimension?

Question

G1 Physics · Accepted Answer

Step 1: For a valid velocity–time graph, each instant t must correspond to only one velocity. Step 2: Image 3 is a closed loop, so for some times it assigns two different velocities to the particle, which is impossible. Step 3: The oscillatory curve in Image 4 is still valid one-dimensional to-and-fro motion. Therefore Image 3 is the invalid graph. Final answer: C. Note: the printed solution label in the source appears inconsistent, but its own explanation identifies option C.